Rhenium, one of the minor metals, is widely used in the fields of catalysts used in reforming petroleum and the production of organic compounds, heat-resistant alloys, and electronic materials. Unfortunately, rhenium is becoming less commonly available because of its low supply and rising world-wide demand in recent years. Such circumstances lead to a demand for development of techniques for efficiently recovering rhenium from minerals containing rhenium and those for recycling rhenium from industrial wastewater or recovered products containing rhenium.
In such a background, for example, Patent Literature 1 discloses a method of separating rhenium. The method involves adding an alkali to a solution containing rhenium and undesired components to remove the undesired components as precipitate, adjusting the concentration of the acid in the solution within a predetermined range, adding a sulfidizing agent to generate sulfide precipitate containing rhenium sulfide, and recovering the precipitate.
Patent Literature 2 discloses a method of recovering rhenium. This method involves adding an ammonium compound, such as ammonium sulfate, to a solution containing rhenium, cooling the solution to generate a precipitate of NH4ReO4, and recovering the precipitate.
Patent Literature 3 discloses a method of recovering rhenium. The method involves adding a compound including a substituent with an atom having an unshared pair of electrons to a solution containing perrhenate ions, irradiating the solution with ultraviolet light to precipitate a reduced species of the perrhenate ions, and recovering the precipitate.